1. Field of the Invention
The present invention relates to a power transmission apparatus employed for an automobile, and more particularly to a power transmission apparatus used in a torque transmitting passage, for example, in a middle of a shaft connecting right and left road wheels and in a middle of a shaft between a front road wheel and a rear road wheel.
2. Description of Relevant Art
In recent years, in a front engine front drive vehicle (FF vehicle), a differential gear having a torque sensitive type limited slip differential function has been reconsidered. When the vehicle is provided with this equipment, a lot of advantageous features can be obtained, for example, a motion performance,of a vehicle is improved, that is, a handling performance is improved, a response against a stepping down operation of an accelerator pedal is improved, a stability of a vehicle motion is improved and the like, so that a mounting rate is increased.
Japanese Patent Publication No. 46-8206 is related to a bevel gear type differential gear.
A differential gear is rotatably supported to a differential carrier (not shown) in boss portions at both ends of a differential case. An inner portion of the differential case is lubricated by an oil in an oil reservoir provided in the differential carrier.
A differential gear mechanism is constituted by a pinion shaft fixed to the differential case, a pinion gear rotatably supported on the pinion shaft and a pair of oppositely arranged side gears meshing with the pinion gear, and the side gears are movably connected to axles, respectively.
Further, clutch members in a pressing side are movably connected onto the axles adjacent to a back surface of each of the side gears and a clutch member in a pressure receiving side is fixed to an inner wall of the differential case. A corn clutch is constituted by both clutch members, thereby performing a limited slip differential operation.
A large opening for assembling the differential gear mechanism and the corn clutches is provided in a cylindrical wall portion of the differential case, and the opening also constitutes a port for a lubricating oil.
However, in general, a housing for accommodating the differential gear is commonly used with a housing for a transmission, and in this case, a lubricating oil of the differential gear is commonly used with that of the transmission. Among the lubricating oil, an AT oil employed for an automatic transmission has a viscosity lower than that of an MT oil employed for a manual transmission, and commonly serves as a working fluid for a hydraulic torque converter. This structure is provided for reducing a frictional loss of the oil flow passage. Further, the viscosity of the AT oil is reduced in the case of being employed for operating the hydraulic actuator. This structure is provided for normally operating the actuator even under a condition that the oil temperature is low.
Further, the AT oil contains an extreme pressure agent. This is provided for improving an abrasion resistance of a drive transmitting surface having a high surface pressure, for example, between a pulley and a belt of a continuously variable transmission (CVT).
Since the differential gear is arranged in a portion after a final reduction of an engine speed under a condition of being dip-feed lubricated by the lubricating oil, a torque corresponding to some times a drive torque transmitted from the engine to the transmission is transmitted. Accordingly, a great force is applied to the slide friction surface and a lubricating oil film can not be kept.
Japanese Utility Model Application Laid-Open (JU-A) No. 5-25038 relates to a sealed type coupling.
A coupling is arranged between a front road wheel and a rear road wheel of a four wheel drive vehicle and distributes a drive force to the front and rear road wheels in correspondence to a difference of a rotational speed generated between the front and rear road wheels. A vane pump is arranged between an input shaft and an output shaft. That is, a rotor of the vane pump is spline connected to the input shaft in the front road wheel side and integrally rotates. On the contrary, a casing is connected to the output shaft in the rear road wheel side and a cam ring is fixed to the casing and integrally rotates with the output shaft.
When the difference of the rotational speed is generated between the front and rear road wheels, the vane pump performs a pump operation together with a relative rotation between the rotor and the cam ring. Accordingly, a hydraulic pressure is generated in correspondence to the difference of the rotational speed between both of the shafts and operates so as to restrict the relative rotation between both of the shafts (between the front and rear road wheels).
At a time of operating the vane pump, the oil in the oil tank provided in the periphery of the casing circulates between the inner portion of the oil tank and the vane pump. The circulating oil is cooled by air within the tank, whereby an abrasion and a seizure of the vane pump are prevented.
However, when an amount of the lubricating oil is not sufficient, the lubricating oil does not sufficiently spread around an engagement portion of the gear, a friction of the engagement portion is increased and a durability of the parts is reduced. Further, a temperature of the lubricating oil is increased, and the lubricating oil is deteriorated. Further, when the viscosity of the lubricating oil is reduced and the great force is applied, the slide lubricating oil film is not kept. Further, an abraded powder generated from the engagement portion of the gear or the like prevents the lubricating oil from flowing, and particularly, reduces a durability of the engagement portion.
A first object of the present invention is to provide a power transmission apparatus in which a lubricating oil suitable for an element constituting an apparatus is used.
A second object of the present invention is to provide a power transmission apparatus which improves a durability of an element constituting an apparatus.
A third object of the present invention is to provide a power transmission apparatus which secures a cooling performance of a lubricating oil.
A fourth object of the present invention is to provide a power transmission apparatus which secures a flowability of a lubricating oil.
A fifth object of the present invention is to provided a power transmission apparatus which improves a durability of an element constituting an apparatus without increasing a size and a weight of the apparatus.
In order to achieve the objects mentioned above, in accordance with the present invention, there is provided a power transmission apparatus employed for a drive train of a vehicle, in which the following features are provided. That is, an outer rotational member has an inner wall surface and an outer wall surface. An inner rotational member is arranged inside the outer rotational member. Friction-clutch means is provided between the inner rotational member and the outer rotational member and is fastened by a thrust force. An oil lubricates at least the friction-clutch means. An oil space intervenes between the inner rotational member and the outer rotational member. Seal means seals the oil in the oil space. A first oil reservoir is recessed on the inner wall surface of the outer rotational member toward a side of the outer wall surface side.
In this case, xe2x80x9cthe power transmission apparatusxe2x80x9d includes, for example, a differential gear mounted in a middle of a shaft connecting drive road wheels and a coupling mounted in a middle of a shaft between a front road wheel and a rear road wheel. Further, a cone clutch type, a structure having a multi disc clutch or a parallel shaft type limited slip differential system is desirable for the differential gear.
xe2x80x9cThe outer and inner rotational memberxe2x80x9d includes a member directly or indirectly rotated by the torque. The outer rotational member is, for example, a housing. The inner rotational member includes, for example, a gear connected to the drive shaft, a hub connected to the propeller shaft, and an intermediate member connecting the drive shaft to the gear, for example, an intermediate shaft.
xe2x80x9cThe oilxe2x80x9d has a different property from AT oil, such as a basic property of an oil, an additive compounded with an oil, and a compounded quantity of an additive component. The oil preferably has a high viscosity property adapted for a friction-clutch.
xe2x80x9cFasteningxe2x80x9d includes a state of fixing the first rotational member and the second rotational member and a state of relatively rotating both the elements.
In accordance with the present invention, the inner portion of the apparatus is separated from the outer portion of the apparatus, and it is possible to use the oil suitable for the inner portion of the apparatus. Further, the differential gear in which the oil: is previously sealed can be transferred as it is and there is no draw back that the oil left within the apparatus leaks out at a time of mounting, so that an assembling operation can be easily performed and a cost thereof can be reduced.
On the contrary, an amount of the oil is increased, and the oil is sufficiently spread around each of the rotational members and a lubricating performance and a flowability can be improved. Further, since a contact area between the oil and the other members is increased, a cooling performance of the oil can be improved.
Preferably, the first oil reservoir has an opening passing through the outer rotational member and a closing member for closing the opening.
In accordance with this structure, the opening can be easily formed and easily closed by the closing member, whereby a first oil reservoir can be secured.
Preferably, the closing member closes only the opening.
In accordance with this structure, the first oil reservoir can be set to a predetermined capacity. Further, an interference with a circumferential member can be prevented.
Preferably, the closing member is an annular member covering the outer wall surface of the outer rotational member.
In accordance with this structure, the number of the parts can be reduced and it is easy to assemble the members. A heat radiating performance of the closing member can be improved and the oil can be more easily cooled. A sealing performance can be improved.
Preferably, the annular member is contacted tight with the outer wall surface of the outer rotational member.
In accordance with this structure, a pressure of the oil to which a centrifugal operation is applied is reduced by a contacting portion and a sealing performance can be improved.
Preferably, the annular member is apart from the outer wall surface of the outer rotational member to define a space portion, and this space portion forms a second oil reservoir.
In accordance with this structure, the sealed oil is increased and a surface area of the annular member is increased, so that a heat radiating performance can be further improved.
Preferably, the power transmission apparatus is further provided with a member to be moved for changing an internal volume of the space portion between the annular member and the outer wall surface of the outer rotational member.
In accordance with this structure, a pressure increase of the oil space can be regulated, and the constituting member within the apparatus, for example, mainly having a friction-clutch is prevented from being abraded due to a heat generation. Further, a heat generation can be restricted and an oil deterioration can be prevented.
Preferably, the power transmission apparatus is provided with a magnetic member fixed to the closing member.
xe2x80x9cThe magnetic memberxe2x80x9d includes a permanent magnet and an electromagnet.
In accordance with this structure, the abraded powders are collected to the magnetic member, so that no bad influence such as a clogging or the like is applied to the sliding portion of the constituting member within the power transmission member mainly having the friction-clutch means. Further, a deterioration of the oil can be restricted.
Preferably, the power transmission apparatus is further provided with an annular seal means interposed between the annular member and the outer wall surface of the outer rotational member.
In accordance with this structure, an assembling performance can be improved and a uniform sealing performance can be obtained all around the periphery.
Preferably, the outer rotational member has a side wall in a direction crossing the rotational shaft, and the first oil reservoir is defined by an inner wall surface of the side wall in an annular shape.
In accordance with this structure, in a radial direction of the outer rotational member, in addition that it is possible to avoid increasing a size, it is possible to secure an amount of oil.
Preferably, the outer rotational member has a side wall in a direction crossing the rotational shaft, and the first oil reservoir has an opening defined by the side wall and an annular second oil reservoir communicating with the opening and arranged adjacent to the side wall.
In accordance with this structure, an amount of sealed oil can be increased. A surface area of the closing member can be increased and a heat radiating performance can be improved.
Preferably, the outer rotational member has a thick portion being thicker than the other portions, and the first oil reservoir is formed within the thick portion.
In accordance with this structure, it is possible to prevent the thick portion from being filled with the heat as well as it is possible to intend to reduce a weight of the apparatus.
Preferably, the thick portion has a protruding portion protruding outside the outer rotational member, and the first oil reservoir is formed within the protruding portion.
In accordance with this structure, an amount of sealed oil can be increased. A surface area of the closing member can be increased and a heat radiating performance can be improved.
Preferably, a plurality of power transmission gears supported along a circumferential direction is provided in the outer rotational member side. The first oil reservoir is formed in the thick portion between the plurality of gears along the circumferential direction.
In accordance with this structure, no new member is required and it is possible to intend to reduce a weight of the apparatus. It is possible to prevent the thick portion from being filled with the heat. It is possible to reduce a rigid body vibration generated by the constituting member such as the gear or the like, and a durability can be improved.
Preferably, the closing member positions the power transmission member arranged in the outer rotational member.
xe2x80x9cThe power transmission memberxe2x80x9d is, for example, a pinion shaft.
In accordance with this structure, since it is not necessary to independently provide a positioning member, the number of the parts can be reduced.
Preferably, the power transmission apparatus is further provided with an electromagnetic clutch, a pilot clutch to be fastened by the electromagnetic clutch, and a cam mechanism for converting a fastening torque of the pilot clutch into a thrust force. The friction-clutch means is a main clutch to be fastened by the thrust force of the cam mechanism. The inner rotational member is a hub arranged in an inner side of the main clutch. The outer rotational member is a case for accommodating the main clutch.
In accordance with this structure, in the power transmission apparatus having a lot of members constituting the friction, it is possible to obtain secure and sufficient lubricating and cooling performance.
Preferably, the power transmission apparatus is further provided with a pinion shaft, and a pinion gear supported to rotate around the pinion shaft. The inner rotational member is a side gear meshing with the pinion gear so as to generate a differential motion. The outer rotational member is a case for accommodating the side gear. The friction-clutch means is a corn clutch to slide between the side gear and the case so as to limit the differential motion.
In accordance with this structure, it is possible to provide a light and compact power transmission apparatus, and a significantly improved mounting performance can be obtained by combining with an automatic transmission (AT).
Preferably, the inner rotational member is a side gear meshing with a pinion gear so as to generate a differential motion. The outer rotational member is a case having an inner hole and supporting the pinion gear to be rotated in the inner hole. The friction- clutch means is to slide between the pinion gear and the case to limit the differential motion.
In accordance with this structure, it is possible to obtain a sealed space sufficiently utilizing a limited space for the apparatus and the apparatus can be established at a high possibility.
Preferably, the power transmission apparatus is provided with a pinion shaft, and a pinion gear supported to rotate around the pinion shaft. The inner rotational member is a side gear meshing with the pinion gear to generate a differential motion. The outer rotational member is a case for accommodating the side gear. The friction-clutch means is a multiple disc clutch provided between the side gear and the case for limiting the differential motion.
In accordance with this structure, in the power transmission apparatus having a lot of members constituting the friction, it is possible to obtain secure and sufficient lubricating and cooling performance.
Preferably, the first oil reservoir is provided in an outer side relative to the friction-clutch means in a radial direction.
In accordance with this structure, an influence applied to the friction-clutch portion by the abraded power can be restricted. This makes it easy to supply the oil to the friction-clutch portion.
Preferably, the first oil reservoir is provided in an outer side relative to the friction-clutch means in a direction of the rotational axis of the outer rotational member and in an inner side of the friction-clutch means in a radial direction of the outer rotational member.
In accordance with this structure, an influence applied to the friction-clutch portion by the abraded power can be restricted. It makes it easy to supply the oil to the friction-clutch.
Preferably, the first oil reservoir is a space formed in an inner portion of the side gear.
In accordance with this structure, an amount of oil can be increased and it is possible to prevent the inner portion of the side gear from being filled with heat.
Preferably, the power transmission apparatus is provided with an accumulator connected to the closing member.
Preferably, the seal means seals an end opening of the inner rotational member in a rotational axis direction.